A circular coil 'A' has a radius R and the current flowing through it is I.Another circular coil 'B' has a radius 2R and if `2I` is the current flowing through it then the magnetic fields at the centre of the circular coil are in the ratio of

Options

A. `4 : 1`
B. `2 : 1`
C. `3 : 1`
D. `1 : 1`

Answer

D

Explanation

Since , `B = (mu_(0) I)/(2r) implies B prop (I)/(r )`
`(B_(1))/(B) = (I)/(R ) xx (2R)/(2I) = 1 :1`